The present invention relates to a printed circuit board and a method of producing the printed circuit board.
The present invention has particular utility in a printed circuit board on which a plurality of signal line conductors are provided to connect a plurality of devices or components which are to be mounted thereon, and on which power supply conductors are formed to provide a power supply to the mounted devices.
An example of such a printed circuit board is a strip-shaped printed circuit board for mounting an array of super-miniature LEDs (light-emitting diodes) therealong. A thick power supply conductor is formed to extend along the length of the strip-shaped printed circuit board, and a plurality of signal line conductors connect respective LEDs to the power supply conductor.
In a prior-art printed circuit board in which the substrate is a glass sheet, the conductors are formed of a thin film of indium-tin oxide (ITO) or tin oxide (SnO.sub.2), and a Ni plating layer and an Au plating layer which are formed in turn, and are patterned by etching. It is also known to form a metal paste layer or a thick metal plating layer over the Ni plating layer to further reduce the electrical resistance.
However, the prior art suffers from substantial variation between the signal line conductors and cannot provide even currents to all the LEDs. The variation can be as much as .+-. about 30%.